Constant current regulator system



April 2, 1957 A. KUSKO 2,787,732

CONSTANT CURRENT REGULATOR .SYSTEM Filed Feb. 16, 1953 ATTOR EY United States Patent CONSTANT CURRENT REGULATOR SYSTEM Alexander Kusko, Brighton, Mass., assignor to Hevi Duty Electric Company, Milwaukee, Wis., a corporation of Wisconsin Application February 16, 1953, Serial No. 337,071

7 Claims. (Cl. 315-179) My invention relates broadly to the regulation of electrical circuits and more particularly to an improved circuit for a constant current regulator.

One of the objects of my invention is to provide a circuit arrangement for a constant current regulator that will limit the rise in current usually obtained with nonlinear loads.

Still another object of my invention is to provide an arrangement of filters which may be interposed between a power supply circuit and the primary circuit of transformer arrangements feeding mixed incandescent and gaseous-lamp loads where the filters operate to suppress harmonic currents so as to limit the rise of the effective lamp current when one or more of the transformers become open circuited.

Other and further objects of my invention reside in a system for transforming constant potential to constant current for both linear and non-linear loads as set forth more fully in the specification hereafter following by reference to the accompanying drawings,-in which:

Figure 1 is a schematic diagram illustrative of the principles of my invention employed in feeding an incandes'cent lamp load; and

Fig. 2 shows a modified circuit arrangement of my invention employed in feeding a mixed incandescent and gaseous-lamp load.

Heretofore in the art, constant current regulators of the monocyclic-square type have not been suitable for delivering constant current to both linear and non-linear loads represented, for example, by an open-circuited street-lighting closed-core insulating transformer. Operating difiiculties with prior regulators have been such that circuits operating on linear loads have shown a rise in output current when non-linear loads have been introduced into the circuit. When a non-linear load, as hereinbefore described, is introduced into the load circuit of a constant current regulator of the static type, it acts like a harmonic generator. When one or more insulating transformers in a series system supplied from a static regulator are open-circuited on the lamp side, the static regulator continues to" circulate, through the transformer primaries, as well as the remainder of the load, approx-imately the same level of C. P. S. current as is circulated under normal condition. However, this current saturates the open-circuited IL transformers and causes them to work as harmonic generators circulating harmonic currents of frequences, 180 C. P. S., 300 C. P. 8., etc., through the load, capacitors of the static regulator, and the line. The net effect is that the effective or R. M. S. current through the still operating lamps arises and may burn them out.

I provide an arrangement of parallel-resonant or tuned L-C filters interposed between the power source and the transformer system for offering a high impedance to the most offending harmonic currents, or to absorb the harmonic voltage and keep the harmonic-current amplitude down. The result will be that the effective or R. M. S. lamp current will rise only a limited amount over its normal 60 C. P. S. value and lamp life will not be endangered. The harmonic voltages generated cause harmonic currents to flow in the circuit comprising the tuned circuit, the power line feeding the regulator and the load. Since the impedance of the tuned circuit to these harmonic voltages is lower than it is for the fundamental, even small harmonic voltages can cause a considerable increase in output current.

The method and apparatus of my invention successfully suppresses harmonic currents in an inexpensive and economical manner due to the small amount of equipment required.

My invention consists in introducing in a series lighting circuit one or. more parallel resonant inductancecapacitance filter circuits tuned to suppress the most offend-ing harmonics in series with the load. This method has been found to be economical of material and practical and efficient in its operation. When constant volt age is impressed across the input of a resonant circuit constant current regulator which includes a tuned circuit consist-ing of reactors and capacitors, the constant voltage is transformed into constant current having the same frequency as the supply voltage. When the load circuit is essentially linear impedance in character, the output constant current is independent of the magnitude of the load impedance. When a non-linear circuit element is introduced, for example, When a lamp in one of the secondaries of one of the insulating transformers burns out and thus causes saturation of the transformer core, a set of harmonic voltages is generated by this open-circuited insulating transformer. These harmonic voltages tend to force harmonic currents through the inciuded filter circuits. Since each filter circuit is tuned to an offending harmonic, it presents a high impedance to the flow of the harmonic current at that frequency and thus prevents the effective current from increasing materially above the nominal value. Thus constant voltage may be transformed, according to the system of my invention, to constant current for both linear and nonlinear loads of the type described. The system of my invention has been found highly practical and successful in operation, and While I have disclosed my invention in one of its preferred embodiments, I desire that the disclosure herein be considered in the illustrative sense and not in the limiting sense.

Referring to Figure 1 of the drawings in more detail, reference character 1 designates an alternating current power supply source such as a l10-volt, 60-cycle alternator delivering constant voltage to the power supply circuit 2-2 across which there is connected the tuned circuits formed in two branches. One branch includes reactor 3 and capacitor 6. The other branch includes capacitor 5 and reactor 4. The constant voltage from line 22 is transformed into constant current in these parallel tuned circuits having the same frequency as the supply voltage. The load circuit is indicated generally at 9 and 10, and since it is essentially a linear impedance, the output constant current is independent of the magnitude of the load. The insulating transformers forming part of the load circuit are represented at 11 and 12 connected, for example, to incandescent lamp-loads 14 and 15. The reactors 3 and 4 and capacitors 5 and 6 are tuned to the fundamental frequency of the supply voltage 1. interposed in series between the series lighting circuit 9-40, including the insulating transformers 11 and 12 and the tuned circuits, I introduce one filter comprising reactor 7 and a capacitor 8 tuned to one of the predominant harmonic frequencies produced by any dis turbance in the operating load represented by transformers 11 and 12, and another filter comprising reactor 16 and capacitor 17 tuned to another predominant harmonic frequency introduced by any disturbance in the operating load.

The operating loads may be the incandescent lamp circuits represented at 14 and 15, as shown in Pig. 1,-or the operating loads may be of ,mixed characteristic such as the incandescent lamp circuit represented at 14 in Fig. 2 and the gaseous discharge tube circuit represented at 18 giving .a varied order of harmonic reactive'voltages when one or the other of the loads fail. That is to say, when one of the lamps burns out and the associated power transformer, such as '11 and 12, becomes saturated, harmonic voltages are generated by this open-circuited insulating transformer. These harmonic voltages tend to force harmonic currents through the line 9., the filter circuits comprising reactor 16 and capacitor 17, reactor 7 and capacitor '8, capacitor 5, power supply circuit 2-2, capacitor 6, output line and the remainder of the load. While part of this harmonic current passes through reactors 3 and .4, it is not necessary to consider this for purposes of this illustration in order to understand the principles of my invention. Since these filters consisting of reactor 16 and capacitor 17 and reactor 7 and capacitor 8 are tuned'to the corresponding offending harmonics, they present a high impedance to the flow of each harmoniccurrent for which there is a-filter and thus prevent the effective current in lines 9 and 10 from increasing materially above the nominal value.

The filter circuits 7-8 and 16-17 are particularly effective when they are tuned to the third and fifth harmonies which are the most predominant and disturbing harmonics. The filter circuits coact to restrict and limit the rise of current in the power distribution circuit 9-10 preventing the burning out of the associated components of the power distribution system. The filter circuits, in effect, suppress harmonic currents so as to limit the rise of the efiective lamp current when one or more insulating transformers become open circuited. The filters are effective only during an emergency condition and are idle under normal circumstances.

I have found the system of my invention highly practical and efiicient in its operation, and while I have described my invention in one of its preferred embodiments, I realize that modifications may be made, and I desire that it be understood that no limitations upon my invention are intended other than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. A constant current regulator system comprising in combination with a source of alternating current, a power distribution system, a multiplicity of power distribution circuits each including a transformer having its primary in series with and energized by said power distribution system, said transformers having loads connected thereto, a closed loop circuit including a pair of branch circuits connected in parallel, each branch circuit including a reactor and a capacitor electrically connected in series, input terminals for said loop circuit at opposite ends of said branch circuits, output terminals for said loop circuit intermediate the reactor and capacitor in each of said branch circuits, connections between said source oi alternating current and said input terminals, connections between said output terminals and said power distribution system, and means connected in said power distribution system tuned to offer high impedance to a harmonic frequency of said source of alternating current developed therein when a load is open circuited.

2. A constant current regulator'system as set forth in claim 1 in which said means connected in said power distribution system consist of a reactance winding shunted by a capacitor and tuned to a harmonic frequency of said alternating source of current.

3. A constant current regulator system comprising in combination with ,a source of alternating current, a power distribution system, a multiplicity of power distribution circuits each including a transformer having its primary connected with and energized by said power distribution system, said transformers having loads connected thereto in their secondary circuits, a closed loop circuit including a pair of branch circuitsconnectedinparallel,each branch circuit including a reactor and a capacitor electrically connected in series,.inpnt terminals for said loop circuit at QPPQsite ends of sai h anch cir ui o p terminals for said loop circuit intermediate the reactor and capacitor in each of said :branch circuits, connections between said :source of alternating current and said input tcrminals, connections between said output terminals and said power distribution system, and a plurality of means connected in seriesand disposed ,in said power distribution system, said means individually tuned to offer high impedance to selected harmonic frequencies of said source of alternating current developed in said power distribution .system when one or more of said secondary circuits reach open circuit condition.

4. A constant current regulator system as set forth in claim 3 in which said means are tuned to otter a high impedance :to the third and fifth harmonic frequencies of the source of alternating current.

5. Aconstant current regulator system comprising an alternating current generator circuit, .a power distribution circuit, I power transformers connected into said power distribution circuit, load circuits connected with the outputs of said power transformers, and a plurality of filter ,circuitsiuterposed between-saidgeneratorcircuit and said power distribution circuit, said filter circuits being tuned to different harmonics of said generator circuit so as to limit current when one of said load circuits is in open circuit condition,

5, A constant current regulator system, as set forth in claim 5, in which said load circuits are constituted by incandescent lamps.

7. .A constant currentrregulator system, as set forth in claim 5, in whichsaid load circuits are constituted by composite lamp systems, one of which is incandescent and another of which is of gaseous discharge characteristic.

R tereuces Cite in the filetof this pat nt UNITED :STAIE-S PATENTS 

